The heir to the O'Farrell Theater pornography empire told a Marin County courtroom that he is not responsible for his girlfriend's death.

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The heir to the Mitchell Brothers O'Farrell Theater pornography empire, on trial for the July 2009 murder of his girlfriend, told an incredulous Marin County courtroom his version of what happened that day.

And it's a doozy.

James Mitchell, 29, was seen beating Danielle Keller, the mother of his three-year old child, to death in the backyard of their Novato home with a metal baseball bat, according to prosecutors and witnesses.

But on the stand, Mitchell -- who inherited the infamous O'Farrell Theater from his father, who incidentally shot and killed his brother and former partner in 1991 -- told the court that two men, one in a white shirt and another in a black shirt, are responsible for the crime.

The mystery men beat him with a bat and ran away with the-then 1-year old child. Mitchell gave chase, rescued his child and escaped in a car. Asked why he never told this version of events to police, investigators, friends, family or anyone else in the world until he told it in court, Mitchell "shrugged," according to the San Francisco Chronicle. "I'm not a murderer," he said.

Mitchell admitted to "beating and slapping" Keller prior to her death, and was served with a restraining order in 2008 that was active the day she died.